I've been invaded by something called "SpySheriff". Ad-Aware SE Personal, Build 1.06r1 goes all the way to 'deleting selection' (including SpySheriff), but then does nothing. The loading icon fills up with bars while it's quarantining selections, then the headline changes to deleting selection, then it just stays the same for hours. I'm new to all this, so I have no clue. Also, I've tried purchasing the code to implement SpySheriff but get nothing but an error-message dead-end. My computer is running slowly, I can run AntiVir and read my email, but my Yahoo browser won't load properly. I'm on DSL, if that's relevant. Ideas, anyone?

You are going to need some special removal tools. Take a look at the self-help instructions here:
http://www.bleepingcomputer.com/forums/topic22402.html